Nitric oxide (NO), along with the other hazardous nitrogen oxides, is known to be involved in and important to many physiologically or clinically important processes. It is also an increasing concern for its environmental impact. Nitric oxide is commonly produced as a byproduct in the combustion processes. Therefore, there is a substantial need for a gas detector that can provide real-time monitoring of nitric oxide, particularly in exhaust gas mixtures, in a sensitive, accurate and economic manner.
Gas chromatography is a scientific method of gas analysis and identification, including trace gas identification such as chemical agent detection. The most sensitive and differentiating gas detectors used in gas chromatography are also the most expensive and bulky. Thus there is the need for less expensive, lighter, highly sensitive and selective gas detectors for gas chromatography.
Gas analysis involves identification and quantification (measuring the partial pressure of each gas) when multiple gases are present in a mixture of gases. The basis of gas identification and quantification for the current invention is emission spectroscopy, which is identification of gases from characteristic light emitted from molecules or atoms. I have developed a nanoliter-sized gas discharge device which causes gases to emit light when they enter a small, high-electric field region. The light from the discharge can be detected by several instruments, including spectrometers (grating or prism based), photodiodes, vacuum photodiodes, and photomultiplier tubes; even the human eye can be used to identify some gases, such as the light emitted from neon (which is the same color emitted by neon signs).
My invention is a micro-discharge device (or an array of devices) through which gas may flow. Gases in the micro-discharge region emit light, which is detected with a photosensor. If there is an array of microdischarge devices, then each micro-discharge device in the detector array has at least one photosensor, and each photosensor may have an optical filter, making it sensitive for a particular wavelength range of interest. Gas may be forced to flow through the device from a pressure differential created by the gas source or from a pump.
Additionally, an electric circuit may be used to monitor the gas discharge characteristics such as a circuit for measuring the voltage or current across the discharge. This measurement can also be used to aid in gas identification since different gases typically have different electronic characteristics.
Fiber optics may be used to direct light from the discharge devices to the optical sensing equipment. My micro-discharge devices have the ability to withstand high temperatures such that they can be used directly in hot gas flow where optical sensing elements often fail to operate. Fiber optics would allow the detector to be located in a chemically reactive and high temperature environment while delivering the light to optical sensing equipment located a few centimeters to a few meters away in a relatively cool ambient atmosphere. This offers another advantage to my detector, that advantage being that little or no gas conditioning needs to be performed before an analysis is made. This speeds the analysis and reduces filtering and pre-conditioning costs.